JPS5855519A - Controlling method for operation of aod furnace with computer simulation - Google Patents

Abstract

PURPOSE:To accurately perform the control of the titled operation, by calculating the substances of components in steel melt and its heat balance, determining a time for charging a coolant, its amount to be charged, a time for switching the composition of refining gas and its amount to be injected, and refining the steel melt. CONSTITUTION:A residual amount of O2 obtained by subtracting an amount of O2 consumed for decarburizing, desilicating and demanganating reactions from an amount of O2 consumed in the interval of an infinitestimal time during the operation of an AOD furnace is considered as an amount of O2 consumed for the oxidation of Cr and the oxidation of Fe with a part of Cr2O3 as the oxidation product. On the other hand, an amount of O2 to be consumed for each of the oxidation of Cr and the oxidation of Fe with a part of Cr2O3 as the oxidation product is calculated from said residual amount of O2 on the basis of the mol ratio of Cr/Fe in slag obtained from data on the actual operation. In this way, the substances of components in the steel melt and its heat balance are calculated, an amount of a coolant to be changed and an amount of refining gas to be injected are determined while measuring the temperature of the steel melt at needs, and refining is performed. The point of time when a predetermined C amount and temperature are obtained is considered as the final point of refining.

Description

[Detailed description of the invention]

The present invention relates to a method for controlling the operation of an AOD furnace, and more particularly, the present invention relates to a method for determining the timing and amount of cold material input in AOD decarburization refining using computer simulation, and a method for controlling the end point of blowing. -For example, the present invention provides a method for operating an AOD furnace for blowing stainless steel by blowing 0□-N2 gas or O8-mr gas, in which the composition and temperature of molten steel are known when injecting molten steel into the AOD furnace. After that, the timing and amount of coating material required for blowing with an arbitrary refining gas composition determined in advance through computer simulation are calculated and determined, and the timing for switching the refining gas composition is also calculated and determined. Furthermore, it relates to a method for controlling the blowing end point based on a model for determining the blowing end point and a calculation program by Hunbueter. According to the conventional analysis method of AOD operation, %Qr-%C-
%0r2o3"""Various analyzes have been carried out on the premise that there is an equilibrium relationship between Co and temperature. However, it is assumed that the region containing higher C than the C in equilibrium with Qr, that is, Qr, will not oxidize. Qr oxidation actually occurs at the same time as O removal even in the range that is normally considered. Therefore, operation using conventional AOD operation analysis means cannot avoid deviations from actual operation, and as a result, accurate operation cannot be carried out. The present invention has the drawback that it is difficult to control the operation accurately, which is caused by the conventional method of controlling the OD operation using the analysis method based on the above-mentioned equilibrium relationship. Eliminate the drawbacks of being
The object is to provide an improved control method, and this object can be achieved by providing the method according to the claims. The present invention solves the problems of Or and F, which were not subject to conventional analysis.
This is based on the new knowledge that the operation is controlled by a computer, taking into account the oxidation phenomenon that deviates from the equilibrium state of e. According to the present invention, in particular, the amount of oxidation (+r) that deviates from equilibrium is determined by the following means. In other words, it is calculated from the product of the concentration difference and the equipment coefficient.The equipment coefficient is determined from the actual measurement data.(b) S soil is also determined in accordance with (ii) above. (c) Mn is also determined in accordance with (a) above. B) The remaining amount of 02 after subtracting the amount of 02 used in the reactions (a) to (c) from the amount of 02 consumed during the minute time interval is used for oxidation of cr and the oxidized Cr2O.
Let it be the amount of 02 consumed in the oxidation of ye by one part of Cr2O3 in 3. (e) 0r20 in slag. oxidizes Fe in the molten steel and produces FeO in the slag. The (3r/li'e (molar ratio)) in the slag at that time is determined from the actual operation data. Calculate the heat balance of molten steel and slag from the change in the amount of each component in molten steel, the change in slag weight, the change in slag component, and the reaction heat in reactions (a) to (e) and the amount of heat released from the AOD container. Then, find the temperature change of the molten steel. (g) According to the above AOD reaction, the molten steel temperature is Since the temperature rises above a predetermined temperature, it is necessary to calculate and determine the amount and timing of application of the coating material in order to suppress such temperature rise.The above calculations are performed in the following order: (a) When the molten steel temperature reaches the predetermined temperature The time when the coating material is added is the time to add the coating material. ■) The amount of the coating material to be added is calculated as follows. The amount of cooling material required to lower the temperature by a predetermined range is calculated by taking into account the heat of reaction within the minute time in (a) to (e) above, the amount of heat released from the reaction vessel, and the heat of melting of the coating material. (0) In order to determine the final time to add the coating material, if it is found that the 0% calculated in (f) above is lower than the C content range determined in advance from actual operation, after that time, the coating material should be added. Finish inputting. (d) On the other hand, the composition of the refining gas is changed as appropriate according to the progress of refining. If the step of swallowing refining gas with the same component composition is considered as one step, the criteria for changing this step is determined as follows. The step is changed when the amount of decarburization determined in (a) above becomes smaller than the desired amount of decarburization. ' □４□□.ゎ ゎ ゎ G 1 1 I l # 1 I between 1,000, 5, and the amount of decarburization commensurate with this. (e) As a result of carrying out the operation according to (C) and (d) above, the end point of the operation is when the predetermined zero amount and temperature are obtained. On the other hand, calculate the amount of Fe-S soil and lime necessary to reduce the oxidized (3r, Mn%F6), and add Fe-8i and lime corresponding to the weight calculated in this way. Transition to the Qr reduction period. The refining method after this is the same as the conventional method. Next, the present invention will be explained with reference to an example. The above-mentioned AOD furnaces have a number of tuyeres of 2 and 1, and the refractories in the furnace are new (the furnace walls are not eroded, so the depth of the steel bath is the same as that of a used furnace. ] and a worn-out furnace in which the refractory in the furnace has been eroded to some extent (the furnace wall is eroded, so the depth of the steel bath is shallower than that in a new furnace). Refining was carried out using each of the furnaces with -4 characteristics. Fig. 1 shows the progress of a computer simulation of operation using a newly built AOD furnace. This is a diagram in which the steel bath temperature (represented by Δ), chromium concentration (represented by ・), and carbon concentration (represented by 0) were investigated over time during the decarburization process. The input times of input materials are shown below, and the types and weights of input materials input at each input time are as follows: ■ HGFeOr 1455 kg ■ Iron scrap
2100 J19 ■ Iron scrap 2000 J9 ■ Stainless steel scrap 2500 to 90aO620
J9 ■ Stainless steel scrap 2ooOkg0aO,,l
, J 610 kg The composition and amount of the gas blown during the above refining were changed as shown in Table 1 below, but if the period of blowing with the same gas composition is referred to as one step, then the refining shown in Figure 1 Gas blowing was performed in two steps of / -41. Next, Table 1 shows the amount and composition ratio of the blown gas in each step. Table 1 Temperature transition (shown by solid line) and [Or)% change (shown by broken line) predicted from the results of calculated values according to the present invention from Table 1
It was found that the ((3)% transition (indicated by the dashed line) and the actual measured values were in very good agreement with each other, proving that the method of the present invention is superior. Slag deposition during operation shown in Figure 1, Feo
This is a calculated value showing the change over time in lMno%0r203 (%).The actual value of the above change over time was not measured because it is very difficult to measure. Example 2 The same method (5US3
Refined 044 stainless steel. FIG. 3 shows a comparison between the simulation using the mathematical model of the present invention and the actual measured values, and the Δ and -10 marks are the same as those in FIG. 7, respectively. In the figure, ■ to ■ indicate the timing of input materials, and the types and weights of input materials input at each input time were as follows. ■ H(tFeOr 1204 J190a0
390719 ■ Fe -Ni 2000 kg ■ Iron scrap
810 I9 ■ re -yi22oo J9 ■ F19- Ni 2000 J90aO51
0 kg ■ Oao 500 kg The composition and composition ratio of the blown gas in each step and the amount of gas for each crack are shown in Table 2. - Temperature transition (shown by solid line) and [Or)% change (shown by broken line) predicted from the results of calculation values according to the present invention from Table 2 and Figure 3
as well as

It can be seen that the [0]% transition (indicated by the one-dot chain line) and the actual measured values match very well. For example n
By adding ayecr, the degree of Ora increases, and l
The situation in which the Qr concentration is diluted and lowered by the injection of t6-IJi (■, ■, ■) is well simulated. Example & A furnace with the same S tuyere as the operating furnace shown in Figure 3 was used, but a new furnace with new refractories was used and the gas amount and gas ratio were operated under the same conditions as shown in Figure 3. . The results are shown in Figure q. In the same figure, ■ to ■ indicate the timing of input materials, and the types and weights of input materials input at each input time were as follows. ■ Iron scrap 950119NiO78
6kg ■ Fe-Ni, 1685 kg
, Iron scrap 510 to 9 QaQ -660719 ■ l'e - Ni 2272 to 9 ■ he -
yiJ2176 kg ■ Oao 500 to 9 ■ Ca056CaO 36O103 kg As can be seen from Figure q, the simulation based on the formula iDel of the present invention and the measured value were in good agreement in this case as well. Calculated values and actual values for the steel bath temperature and steel bath composition after the completion of decarburization in Examples 1 to 3 shown in Figures 1, 3, and q are shown in Table 3, respectively. It can be seen that they match extremely well. Table 3 Implementation side number S Figure S was simulated using the molten steel composition and temperature at the time of receiving AOD steel as the initial conditions, and the actual operation was carried out, but a check analysis and temperature measurement were performed on the way, and the simulation was performed again using these as the initial conditions. This shows the results of modifying operations. In the same figure, ■ to ■ indicate the timing of input materials, and the types and weights of input materials input at each input time were as follows. ■ Fe820 kg NiO786 kg ■ Fe-N1608 to 90aO-r:r9okg ■ Fe -Ni 1533 kg-1e -O
r, 193 kg ■ cao 5
00 kg Fθ-Ni 1731 kg ■Fe-Ni 2476 kgOaO500k
g The dotted line in the figure shows the composition and temperature at the time of AOD receiving as initial conditions, and the simulation was performed, and the check analysis and temperature measurement were performed at the end of 0 cost step, which is the one after blowing. According to this, the temperature of the melt #Ii is 75℃ higher than the calculated value, and the 0 and Cr% are also low, making it a little overoxidized. Therefore, in order to suppress the temperature increase, the dotted line was calculated using the 02 amount at the beginning. In the case of 0, the upstream was also reduced by is% and blown. This calculated value is shown by a solid line, and the operating value is shown by M, ·, 0 (temperature, Qr%, and 0%, respectively). As a result of the modification, it was possible to lower the temperature of the decarburized powder, prevent chromium loss, and avoid overoxidation. Table 4 shows the calculated values of the components and temperature at the end of 2nd step and the end of decarburization when receiving AOD steel, and the actual measured values of the components and temperature at the end of 1st step and the end of decarburization, using these as the initial conditions. The calculated values and actual measured values of the simulated decarburized powder are shown. Although the decarburization is completed by dastep, the simulation and operation results of lr decarburization, in which only murium is injected to promote the reaction between excess oxygen and C in the molten steel, are also shown. Table 5 below shows the gas composition and injection amount during decarburization refining. Table 5 Note * 3 , 45TEP actual operation is 02ii1 from this table.
5% or more reduction According to the present invention, a, which was not subject to conventional analysis,
Considering the oxidation phenomenon that deviates from the equilibrium of r and Fe,
The timing and amount of coating material to be added in decarburization refining using an AOD furnace can be determined by an electronic computer, and the blowing end point can be accurately controlled.

[Brief explanation of the drawing]

FIG. 1 shows an AODlf having a double tuyere according to the method of the present invention.
Figure 1 is a diagram showing the progress of computer simulation of the r-furnace Wl industry. Figure 1 is a diagram showing calculated values of changes in slag weight and FeO%MnO%0r203 (%) over time during the operation shown in Figure 1. Figure 3 is Figure 9 shows the progress of a computer simulation of the operation of an old AOD furnace with J-shaped tuyeres according to the method of the present invention. Fig. 3 is a diagram showing the progress of a computer simulation in which actual operation according to the present invention was carried out, check analysis and measurement was performed midway, and the simulation was performed again using this as an initial condition to correct the operation.

Claims (1)

[Claims] %Qr-%C-%(3r203-P
□ On the premise that there is an equilibrium relationship between temperatures, determine an arbitrary refining gas composition in advance, calculate and determine the timing and amount of coolant input necessary for blowing, and switch the refining gas composition. MoOD by computer simulation that calculates and determines the timing and controls the blowing end point based on the model and program that determines the blowing end point.
In the method for controlling furnace operation, the method includes removing Cl, deSi, and M from the 02 wrinkles consumed during a minute time interval during the AOD furnace operation.
The amount of 02 remaining after subtracting the amount of 02 consumed in the reaction of n is the amount of 02 consumed in the oxidation of Or and the oxidation of F6 by some of the 0r203 in the oxidized Cr2O3. C1rA in the determined slag
? Based on the e molar ratio, calculate the amount of 02 consumed in the oxidation of Qr out of the remaining 02jl and the oxidation of 3e by some Cr2O3 in the oxidized 0r203, and calculate the mass balance of the components in the molten steel. Calculate the heat balance, measure the temperature of the molten steel if necessary, determine the timing and amount of cold material to be introduced, and determine the timing and amount of gas injection to change the refining gas composition. A control method for an AOD furnace operation by computer simulation, characterized in that the point at which the blowing temperature is obtained is set as the blowing end point.